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National Repository of Grey Literature 2 records found  Search took 0.01 seconds. 
Influence of biotic and abiotic factors on population dynamics of a critically endangered species Spiranthes spiralis
 IPSER, Zdeněk
A population of a critically endangered species Spiranthes spiralis was discovered in 1980 in the National Natural Monument Pastviště u Fínů near village Albrechtice, close to Sušice city. Since 1985 the number of flowering individuals in this population has been annually monitored. Since autumn 1998 all the specimen found there have been marked and biometrically measured. During these periods (12 or 26 years, respectively), large year-on-year fluctuations in the number of flowering plants and in the survival of the individual rosettes have been recorded. The main aim of my work was to assess the effect of weather conditions (temperature, precipitation, the number of days of snow) on the population dynamics and on the fitness of plants (leaf area, probability of flowering and probability of death). The year-round lower temperature and the wet end of autumn during the previous year (t-1) together with the wet spring of the following year (t) had a positive effect on the leaf area during the period of maximal rosette growth (end May in the year t). The probability of flowering was positively affected by the lower temperatures in May and June in the previous year (t-1) and in August just before flowering (year t). The probability of death (in the year t) was increased when the March precipitation (in t) and October temperatures (in t-1) were low. The average number of seeds in the capsule was 1528 ? 885 (s.d.). The number of flowers was positively correlated with the number of mature capsules. However, it did not affect the ratio of mature capsules. Capsules developed on average from 44% ? 24.6 % (s.d.) of the flowers. The average life time of individual plant cohorts was 4.7 years. The number of rosettes per each position was variable from 1 to 7 rosettes (73.2% positions had only 1 rosette). The annual life cycle of the underground organs is described at the end of the thesis.
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Use of image analysis in the monitoring of critically endangered species Spiranthes spiralis
 IPSER, Zdeněk
A population of an endangered orchid species Spiranthes spiralis was discovered in 1980 in the National natural monument Pastviště u Fínů in village Albrechtice, near Sušice. Since 1985 the number of flowering individuals of this population has been regularly monitored. Since autumn 1998 all the specimen found there have been marked and biometrically measured. Since the beginning of monitoring, big fluctuations in the number of flowering specimens or in survival of the individual plant rosettes have been observed among the years. The aim of this thesis was to design the so called index of shading and to verify the possibility of its use to explain some phenomena of plant population dynamics. The index was designed with image analysis and biometric data. The hypothesis has been tested, that the basic variable determining the plant{\crq}s fitness (survival, flowering, vegetative propagation etc.) is the rate of shading by neighboring vegetation (expressed with the index of shading). It has been found that the effect of shading on flowering is not significant or hidden by other factors (such as the course of the weather in the season etc.). The size of the leaf area affects the probability of flowering, number of blooms and height of the inflorescence stem. My thesis also focused on costs of flowering, survival probability (since 1998) and flowering dynamics (since 1986).
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